Method of monitoring a vascular access and an apparatus for extracorporeal treatment of blood with a device for monitoring the vascular access

Abstract

A method and device for monitoring a vascular access during a dialysis treatment in which the pressures in both the arterial and venous branches of the extracorporeal blood system are monitored by pressure sensors. Characteristic values for the condition of the vascular access are calculated in a computer unit from the pressures in the arterial and venous branches of the extracorporeal system, and these values are analyzed in an analyzer unit to detect a defective vascular access.

What is claimed is:  
     
       1. A system for extracorporeal blood treatment comprising: 
       (a) an extracorporeal blood path comprising an arterial line in fluid communication with a first vascular access and an inlet to a blood treatment device, and a venous line in fluid communication with an outlet of the blood treatment device and with a second vascular access;  
       (b) an arterial fluid pressure sensor in communication with the arterial line and constructed and arranged for measuring pressure within the arterial line;  
       (c) a venous fluid pressure sensor in communication with the venous line and constructed and arranged for measuring pressure within the venous line;  
       (d) a computer unit connected to the arterial and venous pressure sensors, which is constructed and arranged for generating first and second characteristic values for the integrity of the vascular access from measured arterial and venous pressures;  
       (e) an analyzer unit constructed and arranged for analyzing the integrity of the vascular access by comparing the first and second characteristic values to first and second ranges of predetermined values.  
     
     
       2. The system of claim  1 , wherein generating the first characteristic value includes calculating a sum of the measured pressure in the venous line and the measured pressure in the arterial line according to the equation P S =P VEN +P ART , and generating the second characteristic value includes calculating a difference between the measured pressure in the venous line and the measured pressure in the arterial line according to the equation ΔP=P VEN −P ART . 
     
     
       3. The system of claim  2 , further comprising a memory unit connected to the computer unit, which is constructed and arranged for storing successive pressure sum and pressure difference values calculated by the computer unit and transmitting the stored values to the computer unit. 
     
     
       4. The system of claim  3 , wherein generating the first characteristic value further includes calculating a change in the pressure sum for successive measurements by subtracting the sum for a first measurement from the sum for a second measurement, and generating the second characteristic value further includes calculating a change in the pressure difference between successive measurements by subtracting the difference for a first measurement from the difference for a second measurement. 
     
     
       5. The system of claim  4 , wherein the first characteristic value is calculated by adding the changes in the sum of a predetermined number of successive measurements, and the second characteristic value is calculated by adding the changes in the predetermined number of calculated pressure differences. 
     
     
       6. The system of claim  1 , wherein the analyzer unit is further constructed and arranged for generating a safe response in reaction to characteristic values selected from the group consisting of: 
       (i) a first characteristic value below the first range of values, and a second characteristic value below the second range of values, and  
       (ii) a first characteristic value above the first range of values, and a second characteristic value above the second range of values.  
     
     
       7. The system of claim  6 , wherein the smallest value in the first range of predetermined characteristic values (M 1 ) is less than the smallest value in the second range of predetermined characteristic values (M 2 ). 
     
     
       8. The system of claim  7 , wherein M 1  is −15 mmHg and M 2  is −10 mmHg. 
     
     
       9. The system of claim  6 , wherein the predetermined number of successive measurements is greater than a product of the frequency of arterial and venous pressure measurement and a value for the attenuation of the arterial and venous pressure sensors. 
     
     
       10. The method of claim  7 , wherein the safe response is an alarm selected from the group consisting of visual and audible alarms. 
     
     
       11. The method of claim  7 , wherein the safe response comprises closing a cutoff clamp in the venous line. 
     
     
       12. The method of claim  7 , wherein the safe response comprises interrupting the provision of blood to the extracorporeal blood path. 
     
     
       13. The method of claim  7 , wherein the safe response comprises stopping a blood pump provided in the arterial line. 
     
     
       14. The system of claim  2 , wherein the system is incorporated into a dialysis machine.